Year 10 · Computer Science · Summer 2
Databases and the Year 10 mock · Lesson 5 of 5
Revision: Paper 2 topics 7 to 10
Exam practice7.7 Trace tables7.9 Writing and amending algorithms10.3 Expressions and circuits
Year 10 · Computer Science · Databases and the Year 10 mock · Lesson 5 of 5
You will learn to
- Complete a trace table, a pseudocode task, a logic circuit and an SQL query under time.
- Plan time on Paper 2, leaving enough for the 15-mark scenario question.
- Evaluate your answers with the mark scheme and record why each mark was lost.
Year 10 · Computer Science · Databases and the Year 10 mock · Lesson 5 of 5
Success criteria
You have got it when you can say:
- I can finish four types of Paper 2 question in the time set.
- I can say how many minutes to spend on a 15-mark question.
- I can sort my lost marks into 'did not know', 'misread' and 'careless'.
Year 10 · Computer Science · Databases and the Year 10 mock · Lesson 5 of 5
Retrieval starter
Questions from before. Write your answers, then show them.
- Last lesson
17 MOD 5 is…
A 2B 3C 3.4
A. 2
- Last unit
Which is a low-level language?
A JavaB Assembly languageC Python
B. Assembly language
- Earlier this year
A diamond in a flowchart means…
A A decisionB Input or outputC A process
A. A decision
Year 10 · Computer Science · Databases and the Year 10 mock · Lesson 5 of 5
Key words (1 of 7)
- Algorithm
- A precise, ordered set of steps that solves a problem.
- Program development life cycle
- The four stages of making a program: analysis, design, coding and testing.
- Structure diagram
- A top-down diagram that shows how a system is split into sub-systems.
- Pseudocode
- A structured, code-like way of writing an algorithm that is not tied to one language.
Year 10 · Computer Science · Databases and the Year 10 mock · Lesson 5 of 5
Key words (2 of 7)
- Totalling
- Adding values into a running total, for example Total ← Total + Value.
- Counting
- Adding 1 to a counter each time something happens.
- Bubble sort
- Sorting by comparing neighbouring items and swapping them if they are in the wrong order, pass after pass.
- Validation
- An automatic check that input data is reasonable and follows set rules.
Year 10 · Computer Science · Databases and the Year 10 mock · Lesson 5 of 5
Key words (3 of 7)
- Check digit
- An extra digit calculated from the other digits, used to catch typing errors.
- Trace table
- A table used in a dry run to record the value of each variable as an algorithm runs.
- Logic gate
- An electronic component that takes one or two inputs and gives one output by a fixed rule.
- Truth table
- A table that lists every possible input combination and the output for each one.
Year 10 · Computer Science · Databases and the Year 10 mock · Lesson 5 of 5
Key words (4 of 7)
- Logic circuit
- Two or more logic gates joined together to give one output.
- Logic expression
- A written description of a circuit using gate names, such as X = A AND NOT B.
- NOT
- A one-input gate whose output is the opposite of its input; also called an inverter.
- AND
- A gate whose output is 1 only when both inputs are 1.
Year 10 · Computer Science · Databases and the Year 10 mock · Lesson 5 of 5
Key words (5 of 7)
- OR
- A gate whose output is 1 when at least one input is 1.
- NAND
- NOT AND: the output is 0 only when both inputs are 1.
- NOR
- NOT OR: the output is 1 only when both inputs are 0.
- XOR (EOR)
- Exclusive OR: the output is 1 when the two inputs are different.
Year 10 · Computer Science · Databases and the Year 10 mock · Lesson 5 of 5
Key words (6 of 7)
- Input
- A signal going into a gate or circuit, such as a sensor reading of 1 or 0.
- Output
- The single result signal that comes out of a gate or circuit.
- Working column
- An extra truth-table column holding the output of one gate inside a circuit.
Year 10 · Computer Science · Databases and the Year 10 mock · Lesson 5 of 5
Key words (7 of 7)
- Sum of products
- An expression made by AND-ing the inputs of each row with output 1, then OR-ing those groups together.
The explanation · step 1 of 13 · part 1 of 2
What Paper 2 tests
Paper 2 (Algorithms, Programming and Logic) lasts 1 hour 45 minutes. It has 75 marks.
It covers topics 7 to 10. It ends with a 15-mark scenario question, answered in pseudocode or program code.
| Question type | How to get the marks |
|---|---|
| Trace table | Work one line at a time. Write a value only when it changes. Copy the output exactly. |
| Write pseudocode | Use the exact comparison the question needs, such as > or >=. Indent inside loops and IFs. |
| Logic circuit | Use the standard gate symbols. Draw the expression as given. Do not simplify it. |
| SQL query | Use the exact table and field names from the question. One clause per line. |
The explanation · step 1 of 13 · part 2 of 2
What Paper 2 tests (continued)
Check the paper length on the current Cambridge 0478 syllabus for the year your pupils sit the exam.
The explanation · step 2 of 13 · part 1 of 2
Plan your time
105 minutes ÷ 75 marks = 1.4 minutes per mark. The same rule as Paper 1.
The scenario question: 15 × 1.4 = 21 minutes. Add a few minutes to plan it first.
Leave about 25 minutes for the 15-mark scenario question. Do not spend it all on the early questions.
The explanation · step 2 of 13 · part 2 of 2
Plan your time (continued)
- Read the scenario. Underline every task it asks for.
- Write a short plan: inputs, loops, checks, outputs.
- Then write the code, one task at a time.
The explanation · step 3 of 13 · part 1 of 2
Mark it like an examiner
- Swap scripts with a partner, or mark your own in a different colour.
- Give one tick for each point in the mark scheme. No tick for 'nearly'.
- Write the missing point next to each lost mark.
- Sort every lost mark into one group from the table.
The explanation · step 3 of 13 · part 2 of 2
Mark it like an examiner (continued)
| Why the mark was lost | Fix for next time |
|---|---|
| Did not know | Add it to the RAG list as red. Revise it. |
| Misread the question | Underline the command word and the key numbers before answering. |
| Careless slip | Leave 5 minutes at the end to check trace tables and code. |
| Ran out of time | Use the 1.4 minutes per mark rule. Move on when stuck. |
Why sort lost marks?
Each group has a different fix. More revision does not help with careless slips.
7.7 Trace tables · The explanation · step 4 of 13 · part 1 of 2
What a trace table is
A dry run means working through an algorithm by hand, line by line, without a computer.
A trace table records the dry run. It has one column for each variable, and one for the output.
Write a new value in a column only when that variable changes. Move to a new row when the loop goes round again.
A dry run lets you check an algorithm before it is coded. It also shows exactly where a logic error happens.
7.7 Trace tables · The explanation · step 4 of 13 · part 2 of 2
What a trace table is (continued)
Do not fill every cell. Cambridge mark schemes usually want a value only where it changes. Copying values down is not wrong but takes time and causes mistakes.
7.9 Writing and amending algorithms · The explanation · step 7 of 13 · part 1 of 3
The 15-mark scenario question: plan first
The last question on Paper 2 is a scenario worth 15 marks. Allow about 30 minutes. You may answer in pseudocode, Python, Visual Basic or Java.
Read the scenario twice. Underline every task. Make a numbered checklist and tick each item as you code it.
Sample scenario: a teacher records three tests for each of 30 students. Each test is out of 50. Names are already in `StudentName[1:30]`.
7.9 Writing and amending algorithms · The explanation · step 7 of 13 · part 2 of 3
The 15-mark scenario question: plan first (continued)
7.9 Writing and amending algorithms · The explanation · step 7 of 13 · part 3 of 3
The 15-mark scenario question: plan first (continued)
Marks are given for meeting each requirement. A checklist stops you forgetting one, which is the most common way to lose marks here.
The explanation · 8 more steps
More on the lesson page
The lesson page has the rest of the explanation, step by step:
- Worked dry run
- Be precise, and amend with care
- Model answer in pseudocode and Python
- How the 15 marks are awarded
- From a statement to an expression
- From an expression to a circuit
- From a circuit to an expression
- From a truth table to an expression
Year 10 · Computer Science · Databases and the Year 10 mock · Lesson 5 of 5
Quick quiz · 1 of 3
A record is…
- A The whole table
- B One row: everything about one thing
- C One column
B. One row: everything about one thing
A field is a column; a record is a row.
Year 10 · Computer Science · Databases and the Year 10 mock · Lesson 5 of 5
Quick quiz · 2 of 3
A good primary key is…
- A A date of birth
- B A surname
- C A unique ID number
C. A unique ID number
Two pupils can share a surname or a birthday. An ID is unique.
Year 10 · Computer Science · Databases and the Year 10 mock · Lesson 5 of 5
Quick quiz · 3 of 3
SELECT Name FROM Pupils WHERE Year = 8 ORDER BY Name; shows…
- A All pupils
- B Only the first pupil
- C Year 8 names in alphabetical order
C. Year 8 names in alphabetical order
WHERE filters the rows; ORDER BY sorts them.
Year 10 · Computer Science · Databases and the Year 10 mock · Lesson 5 of 5
Exit ticket
Answer on paper before you go. Then check.
The data type for 'has paid' (yes or no) is…
A TextB BooleanC Real
B. Boolean Boolean holds true or false.
SELECT COUNT(*) FROM Pupils WHERE House = 'Red'; gives…
A How many pupils are in RedB Their namesC The total score
A. How many pupils are in Red COUNT gives one number: how many records match.
Year 10 · Computer Science · Databases and the Year 10 mock · Lesson 5 of 5
Homework and the challenge
Homework
The CS 9 quiz; one past paper over the summer, self-marked.
End-of-unit challenge
Year 10 mock: a full Paper 1 or a full Paper 2 (1 hour 45 minutes), marked with the Cambridge mark scheme.